1. Field of the Invention
This invention relates to an elastomeric bushing, and more particularly, to such a bushing having a long useful life when subjected to high, substantially unidirectional load levels.
2. Description of the Prior Art
Elastomeric bushings are in widespread use where relative rotational motion is required between a member in contact with the outer surface of the bushing and a member in contact with the inner surface of the bushing. The usefulness of such bushings in supporting a load between the outside and the inside surfaces thereof is a function of the compression strength of the elastomer and the angle of rotation between the outer and inner surfaces together with the speed of the change in such rotational position. An elastomeric bushing is preferable to sliding or roller bearings in many applications because no lubrication is required and inherent isolation from shock and vibration loading is provided.
One such prior art elastomeric bushing is shown in FIG. 1A of the drawings wherein a central hollow cylindrical metal core and an outer split metal ring has a rubber cylinder bonded to the facing surfaces therebetween. However, it has been found that the rubber bushing of FIG. 1A dictates that a severe tolerance be maintained on the dimension defining the bore which receives the elastomeric bushing. Moreover, the assembly process for the bushing of FIG. 1A is relatively expensive since it must include bonding of the elastomer over 100% of the contact area between the split rings and the elastomer as well as over 100% of the contact area between the cylindrical core and the elastomer.
FIG. 1B shows an alternative form of prior art rubber bushing wherein continuous outer and inner cylinders have an elastomeric cylinder positioned therebetween. The type of bushing represented in FIG. 1B typically is not bonded to the outer or the inner metal sleeves but is merely pressed over the inner sleeve and into the outer sleeve at the same time. This type of bushing must generally be retained axially within an accepting bore by some independent structure.
FIG. 1C shows a further prior art rubber bushing which has a hollow metallic inner sleeve and spaced elastomeric rings bonded to the outer surface thereof. The bushing of FIG. 1C is pressed into a receiving bore so that torque applied to the inner sleeve of the bushing induces relative rotational motion between the wall of the bore and the inner sleeve. The capacity for withstanding load without deterioration of the elastomer in the spaced rings is the same in the bushing of FIG. 1C for any radial direction of load applied thereto. The magnitude of the maximum load which may be applied radially to the spaced ring bushing is limited because the bonded area of the surface of the elastomer within which the load energy is dissipated is reduced by virtue of the spaced ring construction. Unbonded surfaces tend to rub and create heat from friction, and also do not support the elastomer at the mating surfaces to prevent high tensile stress from occurring therein.